Unilateral congenital agenesis of sternocleidomastoid and trapezius muscles is a rare occurrence. To date, there are only two case reports in the literature. We present a case of a 7-year-old Caucasian boy who was born with torticollis and a cosmetic defect in his neck. An MRI scan of the cervical spine and shoulder confirmed the absence of the right sternocleidomastoid and trapezius muscles. No other significant congenital anomalies were detected. The patient has been followed-up for 7 years with no functional disabilities.